Because there's no crying in space. You literally can't cry. According to a recent tweet by astronaut Chris Hadfield, "your eyes make tears but they stick as a liquid ball," aggregating into a salty spherule that stings the eyes and blurs the vision.

The Atlantic's Megan Garber has the whole scoop on crying in low Earth orbit, including some interesting ruminations on the unaccountable sting of space tears:

Tears, in theory, shouldn't hurt. We don't know why, exactly, we cry, but we're pretty sure that the action, evolutionarily, has a palliative effect. Tears should soothe, not sting. But we know as well that life in near-zero-gravity can have a deleterious effect on human vision — and one explanation for that could be fluids shifting toward the head during long-term stays in microgravity. It could be that space gives you a pretty wretched case of dry eye — and that sudden moisture to the cornea, particularly when it takes the form of (eeesh) "a liquid ball," could sting rather than soothe.